Radioactive seed with multiple markers and method for using same

ABSTRACT

A radioactive seed which discloses the orientation and the location of the seed when the seed is exposed to X-ray photography is provided. The seed contains multiple X-ray detectable markers which will disclose the orientation and the location of the seed when the seed is exposed to X-ray photography. The seed can also have a single marker which wraps around the external surface of the seed or wraps around a carrier body within the seed. The single marker will also disclose the orientation as well as the location of the seed.

[0001] This is a continuation-in-part of U.S. patent application Ser.No. 08/904,695, filed on Aug. 1, 1997.

FIELD OF THE INVENTION

[0002] This invention relates to radioactive seeds and, in particularembodiments, to improved radioactive seeds for treating diseased tissueswith radiation therapy.

BACKGROUND OF THE INVENTION

[0003] Over the years, brachytherapy sources implanted into the humanbody have become a very effective tool in radiation therapy for treatingdiseased tissues, especially cancerous tissues. The brachytherapysources are also known as radioactive seeds in the industry. Typically,these radioactive seeds are inserted directly into the tissues to beirradiated using surgical methods or minimally invasive techniques suchas hypodermic needles. These radioactive seeds typically contain aradioactive material such as iodine-125 which emits low energy X-rays toirradiate and destroy malignant tissues without causing excessive damageto the surrounding healthy tissue, as disclosed by Lawrence in U.S. Pat.No. 3,351,049 ('049 patent). Because radioactive materials likeiodine-125 have a short half-life and emit low energy X-rays, theradioactive seeds can be left in human tissue indefinitely without theneed for surgical removal. However, although radioactive seeds do nothave to be removed from the embedded tissues, it is necessary todetermine the position and the number of radioactive seeds implanted ina patient's tissue to effectively treat the patient. This information isalso useful in computing the radiation dosage distribution in the tissuebeing treated so that effective treatment can be administered.

[0004] In the '049 patent, the radioactive seed includes a therapeuticamount of radioisotope appropriately distributed on a carrier body. Thecarrier body is sealed inside an elongated cavity of a capsule toprevent the radioisotope from interacting with body fluids while at thesame time permitting the radiation to pass through the walls of thecapsule. Furthermore, to allow X-ray detection of the radioactive seed,the radioactive seed contains an X-ray marker made of a dense, highatomic number material, such as gold, which can block the transmissionof X-rays so that the radioactive seed can be detected by using X-rayphotographic techniques. The capsule, which is typically made out of alow atomic number material, cannot be detected using X-ray photographictechniques because low atomic number materials allow X-rays andradiation to pass through them, instead of blocking X-rays andradiation.

[0005] The '049 patent discloses two methods of providing an X-raymarker. In one method, a small ball constructed of a dense, high atomicnumber material, such as gold or tungsten, is provided in between twocylindrical carrier bodies impregnated with a radioisotope. In anothermethod, a wire made of a high atomic number dense material is locatedalong the central axis of symmetry of the carrier body that isimpregnated with a radioisotope. Both the X-ray marker and the carrierbody are encapsulated and sealed within a low atomic numbered materialcontainer or a capsule which minimally absorbs the radiation emitted bythe radioisotope.

[0006] Although the above-described methods of providing an X-ray markerare effective in detecting the radioactive seed, they have certainproblems. In the first method in which a small ball is provided as aX-ray marker, the ball just appears as a circular dot on an X-ray filmand does not provide any information as to the orientation of theradioactive seed. Since the orientation of the radioactive seed is notknown, the radiation dosage distribution cannot be computed accurately.In the second method in which a centrally located wire is provided as anX-ray marker, the orientation of the radioactive seed can be determined.However, the second method presents manufacturing problems, such aspositioning the wire centrally at the axis of symmetry, which can raisethe cost of manufacturing the radioactive seeds.

[0007] In other radioactive seeds such as one disclosed by Kubiatowiczin U.S. Pat. No. 4,323,055 ('055 patent), a long cylindrical rod-likemember located centrally within the seed is usually employed as an X-raymarker. In the '055 patent, a silver rod coated with iodine-125 isemployed as an X-ray marker. Although such X-ray markers like the silverrod in the '055 patent may disclose the orientation of the seed, thesilver rod in the '055 patent is coated with the iodine-125 byperforming a complicated chemical process which in turn will complicatethe overall manufacturing process and raise the cost of manufacturing.As discussed above, the orientation of the seed can be very important incomputing the radiation dosage distribution. Therefore, simpler and morecost effective apparatuses and methods are needed in providing X-raymarkers which will disclose the orientation of the radioactive seed whenthe seed is exposed to X-ray photography.

SUMMARY OF THE DISCLOSURE

[0008] It is an object of an embodiment of the present invention toprovide an improved radioactive seed for use in radiation therapy, whichobviates for practical purposes, the above-mentioned limitations.

[0009] It is also an object of an embodiment of the present invention toprovide a system for monitoring radioactive dosages in affected tissuein brachytherapy.

[0010] It is also an object of an embodiment of the present invention toprovide simple and cost effective X-ray detectable markers which willdisclose the orientation of the radioactive seed when the seed isexposed to X-ray photography.

[0011] According to an embodiment of the present invention, aradioactive seed for use in radiation therapy includes a sealed housinghaving an internal cavity, at least one carrier body disposed within thecavity for maintaining and distributing a radioisotope along the lengthof the cavity and a plurality of X-ray detectable markers distributedamong the at least one carrier body such that the distribution of theX-ray detectable markers discloses the orientation of the radioactiveseed when the seed is exposed to X-ray photography.

[0012] In particular embodiments of the present invention, the carrierbody comprises a plurality of separate carrier units in which each ofthe carrier units is impregnated with the radioisotope. The carrierunits are evenly distributed along the length of the cavity so that theseed emits substantially uniform radiation around the sealed housing ofthe seed. However, in alternative embodiments, the carrier units can beconcentrated at one end of the seed. In addition, the X-ray detectablemarkers are distributed among the carrier units so that the markers willdisclose the orientation of the seed when the seed is exposed to X-rayphotography. Both the X-ray detectable markers and the carrier unitspreferably have a substantially spherical shape like a ball or a bead sothat the markers and carrier units can be easily rolled into the cavityof the housing during the manufacturing process.

[0013] In other embodiments of the present invention, the X-raydetectable marker wraps around the carrier body or the sealed housing ina spiral shape to reveal the location and the orientation of theradioactive seed. In other embodiments of the present invention,radioactive seeds have different configurations of X-ray detectablemarks for identifying a particular type of radioactive source in theseed or dosage level.

[0014] Other features and advantages of the invention will becomeapparent from the following detailed description, taken in conjunctionwith the accompanying drawings which illustrate, by way of example,various features of embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWING

[0015] A detailed description of embodiments of the invention will bemade with reference to the accompanying drawings, wherein like numeralsdesignate corresponding parts in the several figures.

[0016]FIG. 1a is a cross-sectional view of a radioactive seed inaccordance with a first embodiment of the present invention.

[0017]FIG. 1b is a cross-sectional view of a radioactive seed inaccordance with a second embodiment of the present invention.

[0018]FIG. 2 is a cross-sectional view of a radioactive seed inaccordance with a third embodiment of the present invention.

[0019]FIG. 3a is a cross-sectional view of a radioactive seed inaccordance with a fourth embodiment of the present invention.

[0020]FIG. 3b is a cross-sectional view of a radioactive seed inaccordance with a fifth embodiment of the present invention.

[0021]FIG. 3c is a cross-sectional view of a radioactive seed inaccordance with a sixth embodiment of the present invention.

[0022]FIG. 3d is a cross-sectional view of a radioactive seed inaccordance with a seventh embodiment of the present invention.

[0023]FIG. 4 is a side view with a partial cross-sectional view of aradioactive seed in accordance with a eighth embodiment of the presentinvention.

[0024]FIG. 5 is a cross-sectional view of a radioactive seed inaccordance with a ninth embodiment of the present invention.

[0025]FIG. 6 is a cross-sectional view of a radioactive seed inaccordance with a tenth embodiment of the present invention.

[0026]FIG. 7a through 7 d show cross-sectional views of radioactiveseeds with different marker configurations to identify particularradioactive sources and dosage levels within the seeds.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] As shown in the drawings for purposes of illustration, theinvention is embodied in a radiation seed. In preferred embodiments ofthe present invention, the radiation seed is used in the human body.However, it will be recognized that further embodiments of the inventionmay be used in animals or other applications where radiation and markersare required.

[0028] Referring to FIG. 1a, a radioactive seed 1 in accordance with afirst embodiment of the present invention includes a tubular containeror a housing 5 with an internal cavity 22 which contains a therapeuticamount of radioisotope 15 evenly distributed on a carrier body 20 alongthe length of the cavity 22. In addition, X-ray detectable markers 10 aand 10 b are disposed at two ends of the carrier body 20, respectively,and the housing 5 is sealed at two ends 25 and 26 to prevent theradioisotope 15 from interacting with body fluids while the seed 1 isimplanted within a human tissue.

[0029] As shown in FIG. 1, the housing 5 isolates the radioisotope 15and the X-ray detectable markers 10 a and 10 b from body fluids bycompletely encapsulating the radioisotope 15 and the markers 10 a and 10b. Therefore, the material for the housing 5 needs to be a non-toxicmaterial that will not interact physically or chemically with bodyfluids. Otherwise, the housing 5 needs a coating of non-toxic materialthat will prevent interaction between the housing 5 and body fluids. Inaddition, the housing 5 should be constructed of a material which willnot significantly attenuate the radiation emitted by the radioisotope 15while having sufficient mechanical strength to allow the implantation ofthe seed 1 into the human body using hypodermic needles or otherappropriate instruments. High atomic number material such as gold orplatinum may have sufficient mechanical strength and the requisitenontoxicity, but high atomic number materials like gold will absorb andattenuate a significant amount of radiation emitted by the radioisotope15 so that effective treatment cannot be administered to a patient.Thus, high atomic number material is not a suitable material for thehousing. However, low number atomic metal such as stainless steel ortitanium has the requisite nontoxicity, sufficient mechanical strengthand the requisite minimal absorption characteristic to preventsignificant attenuation of the radiation emitted by the radioisotope 15.In alternative embodiments, medical grade plastics, ceramics, or thelike may be used.

[0030] Titanium has a high strength-to-weight ratio and a low atomicnumber, in addition to being exceptionally corrosion resistant andnon-toxic. Thus, titanium is a very suitable material for the housing 5.The wall thickness of the titanium may vary from 0.001 of an inch to0.005 of an inch while the attenuation is about 5-7% per thousandths ofan inch for low energy X-rays, such as from iodine-125 or palladium-103,and would be lower for higher energy photons. An optimum value of wallthickness is approximately 0.002 inch. However, smaller or largerthicknesses may be used, with the thickness being dependent on thelocation of use, the amount of radiation and the type of radioactivematerial. The ends of the titanium housing can be sealed by usingvarious techniques known in the industry such as laser welding or thelike. Such a technique is described in U.S. patent application Ser. No.09/048,517, entitled “Laser Welded Brachytherapy Source and Method ofMaking the Same,” filed on Mar. 26, 1998, assigned to North AmericanScientific, Inc., and incorporated herein by reference. In alternativeembodiments, the ends may be sealed by a cover secured by adhesives orcrimping.

[0031] The housing 5 should be preferably designed for implantationusing hypodermic needles or other similar instruments designed forimplanting the seed 1. As a result, the housing 5 preferably has a long,thin elongated shape with an outer diameter of about 0.5 to 1 millimeterand a length of about 4-5 millimeters to allow the seed 1 to passthrough a hypodermic needle. However, smaller or larger diameters may beused, with the diameter being dependent on the location and applicationin which the seed will be used.

[0032] As mentioned above, the housing 5 has an inner cavity 22 whichcontains a carrier body 20. In preferred embodiments, the carrier body20 is an ion exchange resin material impregnated with the radioisotope15. The carrier body 20 is used to concentrate, collect and support theradioisotope 15 so that the radioisotope 15 can be evenly distributedalong the length of the cavity 22 to prevent having a point source whichcan prevent effective treatment. The carrier body 20 generally conformsto the shape of the inner cavity 22 so that the carrier body 20 can beeasily inserted into the cavity 22 during the manufacturing process. Thecarrier body 20 can be constructed from any suitable material that canbe impregnated with the radioisotope 15 and that can allow evendistribution of the radioisotope 15 along the length of the seed 1.However, the carrier body 20 should be preferably constructed from a lowatomic number material since high atomic number material can absorb theradiation from the radioisotope 15. In alternative embodiments,plastics, ceramics, composites, low atomic number metals and the likemay be used as carrier bodies.

[0033] In preferred embodiments, the material for the radioisotope 15should be chosen from a material which has a radiation energy in thesoft X-ray region, from about 20 to 100 Kev and a half-life of about 5to 100 days. If the material has a half-life shorter than 5 days, thenthe material will tend to dissipate before it can be packaged andshipped, and if the material has a half-life longer than 100 days, thenthe radioactive seed may have to be removed surgically since the seedmay emit radiation even after the treatment period is over. Materialssuch as iodine-125 or palladium-103 can serve as a suitable radioisotopematerial for the radioisotope 15 since both iodine-125 and palladium-103have a radiation of approximately 30 Kev energy X-rays and possess ahalf-life of about 60 days and a half-life of about 10 days,respectively. However, in alternative embodiments, other materials andhalf-lives may be used, with them being dependent on the treatmentperiod, the radiation intensity needed and the location where the seed 1will be placed.

[0034] In addition to having the carrier body 20 impregnated withradioisotope 15, the cavity 22 also contains a plurality of X-raydetectable markers 10 a and 10 b. The X-ray detectable markers 10 a and10 b are each disposed adjacent to the two ends of the carrier body 20,respectively. However, instead of using just two X-ray detectablemarkers, more than two X-ray detectable markers may be used. By havingtwo or more X-ray detectable markers, the orientation of the seed 1 canbe detected, as well as the location of the seed 1, when the seed 1 isexposed to X-ray photography. Since the X-ray detectable markers 10 aand 10 b reveal two ends of the seed 1, the orientation of the seed 1can be determined based upon the locations of the X-ray detectablemarkers 10 a and 10 b. In other words, the orientation of the seed 1 canbe determined from a line intersecting the X-ray detectable markers 10 aand 10 b. By disclosing the orientation of the seed 1 in addition to itslocation, the preferred embodiments of the present invention may alsoallow for more accurate determination of the radiation dosagedistribution in the tissue being treated so that a more effectivetreatment can be administered. As mentioned above, any multiple numberof X-ray detectable markers can be employed to disclose the orientationof the seed 1. For example, instead of just having one marker at eachend of the carrier body 20, two markers can be placed adjacent to eachend of the carrier body 20.

[0035] In preferred embodiments of the present invention, the X-raydetectable markers have a substantially spherical shape like a bead or aball so that the markers can be easily rolled into the inner cavity 22to facilitate the manufacturing process and reduce the manufacturingcost. However, in alternative embodiments, other shapes, such ascylinders or the like, may be used so long as manufacturing is notimpeded. The X-ray detectable markers are preferably constructed from adense, high atomic number material, such as gold or tungsten, which willblock the transmission of X-rays so that the X-ray detectable markerswill appear on an X-ray film used in X-ray photography. However, inalternative embodiments, other materials such as lead or uranium may beused so long as X-rays are blocked and there is no health hazard fromtheir use.

[0036] The diameter and the size of the X-ray detectable markers arepreferably sufficiently large to allow X-ray detection (i.e., appear onthe X-ray film), but the markers are preferably appropriately sized sothat the markers would not attenuate the radiation emitted by theradioisotope 15. If a large amount of dense, high atomic number materialis used as X-ray detectable markers, then the markers would severelyattenuate the radiation emitted by the radioisotope and decrease theeffectiveness of the seed. However, as seen in FIG. 1, the X-raydetectable markers 10 a and 10 b are located at two ends of the seed1and would absorb only a small amount of the radiation emitted by theradioisotope 15. Since the two markers 10 a and 10 b are located at twoends of the seed 1, the uniformity of the radiation emitted around thehousing 5 of the seed 1 is only slightly affected.

[0037]FIG. 1b shows a radioactive seed 2 in accordance with a secondembodiment of the present invention. The radioactive seed 2 is similarto the radioactive seed 1 except that the seed 2 has a carrier bodydivided into two separate portions 20 a and 20 b. In addition, the seed2 has another X-ray detectable marker 11 c in between the two portions20 a and 20 b. Therefore, the seed 2 has three X-ray detectable markers11 a, 11 b and 11 c. By having a third marker in the middle, themid-section of the seed 2 can be easily determined, and the seed becomesmore readily identifiable.

[0038]FIG. 2 shows a radioactive seed 30 in accordance with a thirdembodiment of the present invention. A radioactive seed 30 has a housing40, a cavity 47, two ends 48 and 49, and X-ray detectable markers 35 a,35 b and 35 c which are similar to the housing 6, the cavity 21, the twoends 23 and 24, and the X-ray detectable markers 11 a, 11 b and 11 cshown in the embodiment of FIG. 1b. However, in FIG. 2, instead ofhaving just one carrier body, a carrier body 45 is divided into multipleseparate components or units, and each of the separate carrier units isimpregnated with the radioisotope 15. Each unit of the carrier body isused to concentrate, collect and support the radioisotope 15 and isdistributed substantially evenly along the length of the cavity 47. Inpreferred embodiments, each carrier body unit is constructed of the samematerial as the carrier body 20 in the previous embodiment and has asubstantially spherical shape like a bead or a ball so that each carrierbody unit can be easily rolled into the cavity 47, just like the X-raydetectable markers, to facilitate the manufacturing process. Thedimension of each carrier body unit and the number of the carrier bodyunits can be appropriately adjusted according to the dimension of thecavity 47 and according to the desired amount of radiation emitted bythe radioactive seed 30. However, as previously mentioned, the carrierbody units should be distributed evenly along the length of the cavity47 to ensure that the seed 30 emits substantially uniform radiationaround the housing 40 of the seed.

[0039] In addition to having multiple carrier body units, a multiplenumber of X-ray detectable markers are distributed evenly among thecarrier body units to disclose the orientation and the location of theseed 30 when the seed 30 is exposed to X-ray photography. As shown inFIG. 2, the X-ray detectable markers 35 a and 35 c are disposed adjacentto the two ends 48 and 49 while the marker 35 b is disposed in themiddle of the cavity 47. The number and the'location of the X-raymarkers should be adjusted appropriately depending on the circumstances,but there should be at least two markers in the cavity 47 to allow fordetermination of the orientation of the seed 30, as discussed above.

[0040]FIGS. 3a-3 d show various different embodiments of the presentinvention. Each of the embodiments shown in FIGS. 3a to 3 d has a uniquearrangement of the carrier body 45 and the X-ray detectable markers 35.FIG. 3a shows a radioactive seed smaller than the previous embodiments.The fourth embodiment shown in FIG. 3a has a single unit carrier bodywith two X-ray detectable markers. FIG. 3b shows a fifth embodiment of aradioactive seed in which the X-ray detectable markers are-disposed inbetween the separate units of the carrier body instead of being placedat the two ends. This facilitates radiation being emitted by the end ofthe seeds. FIG. 3c shows a sixth embodiment in which there are two X-raydetectable markers and two carrier body units arranged in alternatingfashion. FIG. 3d shows a seventh embodiment of a radioactive seed inwhich the carrier body units are concentrated at one end of the seedinstead of being evenly distributed along the length of the innercavity. Such radioactive seeds can be useful in situations where theradiation has to be concentrated at certain points. Also, the X-raymarkers could serve to block radiation in one direction and helpminimize radiation effects on healthy tissue. In addition, because theX-ray detectable markers are disposed at the other end of the seed, oneend of the seed can be differentiated from the other end when the seedis exposed to X-ray photography.

[0041]FIG. 4 shows an eighth embodiment of the present invention. Aradioactive seed 60 shown in FIG. 4 has a housing 70, a cavity 67 andtwo ends 77 and 78 similar to the ones in the previous embodiments. Theseed 60 has a carrier body 65 comprised of multiple separate unitssimilar to the embodiment shown in FIG. 2, but the carrier body 65 maybe a single piece similar to the carrier body 20 shown in FIG. 1a. Incontrast to the previous embodiments, the seed 60 has an X-raydetectable marker 75 which wraps around the full length of the externalsurface of the housing 70 like a spiral or a cork screw. Since themarker 75 wraps around the full length of the housing 70, the marker 75will disclose the orientation of the seed 60 as well as its locationwhen the seed 60 is exposed to X-ray photography. However, the spiralmarker still permits radiation to be emitted through the spaces in thespiral or corkscrew. In alternative embodiments, the X-ray detectablemarker 75 may be formed as an integral part of the housing or placed inthe interior of the cavity 67 so long as the X-ray detectable marker 75will not interfere with manufacturing or placement of the seed.

[0042]FIG. 5 shows a ninth embodiment of the present invention. Aradioactive seed 80 has a housing 81, a cavity 82 and two ends 87 and 88similar to the ones in the previous embodiments. However, the seed 80has a single carrier body 90 disposed in the cavity 82 and an X-raydetectable marker 85 which wraps around the full length of the carrierbody 90 in a spiral shape. Since the marker 85 wraps around the fulllength of the carrier body 90, the marker 85 will also disclose theorientation of the seed 80 as well as its location when the seed 80 isexposed to X-ray photography.

[0043]FIG. 6 shows a tenth embodiment of the present invention. Aradioactive seed 100 has a housing 102, a cavity 104 and two ends 108and 109 similar to the ones in the previous embodiments. The seed 100also has a carrier body 110 comprised of multiple separate units similarto the embodiment shown in FIG. 2, but the carrier body 110 may be asingle piece similar to the carrier body 20 shown in FIG. 1a. Incontrast to the previous embodiments, the seed 100 has X-ray detectablemarkers 105 which have a substantially cylindrical shape with a holethrough the long axis of the X-ray detectable markers 105. The hole inthe middle allows the radiation from the carrier body 110 to passthrough the markers 105 so that the ends 108 and 109 will also emitradiation. In many instances, the ends 108 and 109 tend to be thickerthan other parts of the housing 102 since the ends have to be weldedafter the carrier body 110 and the X-ray detectable markers 105 areinserted into the cavity 104. Consequently, less radiation may passthrough the ends 108 and 109. By having substantially cylindrical holesin the X-ray detectable markers 105, more radiation will be able to passthrough the ends 108 and 109 to alleviate the problem stated above. Infurther embodiments, the X-ray detectable markers 105 can also bemodified such that the markers will be able to slide over a single piececarrier body. In other words, the carrier body can be inserted into thehole of the markers so that the markers can be positioned over any partof the carrier body.

[0044]FIGS. 7a through 7 d illustrate how different markerconfigurations within a radioactive seed can identify the type ofradioactive sources in the seed and the dosage level of the seed. Eachof the seeds 128, 130, 132 and 134 include at least two radioactivemarkers 120 in a particular configuration to identify the radioactivesource in the seed and the dosage level. FIG. 7a and 7 b showcross-sections of seeds 128 and 130 having palladium-103 as aradioactive source in respective sets of carriers 122 and 124. Seed 128includes three adjacent spherical X-ray markers 120 a centered in theseed, leaving two radioactive carriers 122 on each side of the threeX-ray markers 120 a. In this embodiment, this particular configurationidentifies the seed 128 as having palladium-103 as the radioactivesource at a dosage of about 0.3 millicuries. Seed 130 has the samemarker configuration of that of FIG. 7a except that the center X-raymarker 120 a is replaced with a carrier 124. This particularconfiguration also identifies the source as palladium 103 but at adosage of about 3.0 millicuries. The different marker configurations inseeds 128 and 130 are preferably detectable in X-ray imaging and allowthe treating physician to distinguish the radioactive seeds implanted inthe affected tissue region with the lower dosage from those implantedseeds having the higher dosage.

[0045] The radioactive seeds 132 and 134 of FIGS. 7c and 7 d includerespective sets of carriers 126 and 136 for providing an iodine-125radioactive source. The radioactive seeds 132 and 134 also each includeX-ray markers 120 at each opposite end of the respective radioactiveseed. With X-ray imaging, the treating physician can distinguish thoseimplanted radioactive seeds having radioactive markers at opposite endsof the seeds, corresponding with seeds having an iodine-125 source, fromthose seeds which do not have radioactive markers at opposite ends ofthe seeds, corresponding with seeds having a palladium-103 source. Also,in addition to having X-ray markers 120 c at opposite ends of thecapsule, the radioactive seed 132 also includes an X-ray marker 120 c inthe center of the capsule. The radioactive seed 134, on the other hand,does not include an X-ray marker in the center of the capsule. Thisallows the treating physician to distinguish implanted iodine-125 seedshaving dosages of 0.3.millicuries, with the X-ray marker in the centerof the capsule, from the implanted iodine-125 seeds having the 3.0millicurie dosage, with no X-ray marker in the center of the seed.

[0046] The embodiments illustrated in FIGS. 7a through 7 d enable thetreating physician to better control and monitor the brachytherapyprocess in an affected tissue area by using different types of isotopes(e.g., iodine-125 or palladium-103) and using different levels ofdosages in the radioactive seeds. This allows the treating physician toproperly dose the core and periphery areas of the affected tissue. Forexample, a potential problem in prostrate brachytherapy is theoverdosing of the core area with radiation and the under dosing of theperiphery areas. The embodiments illustrated with reference to FIGS. 7athrough 7 d permit the accurate identification of the activity resultingfrom the implanted seeds at both the core and periphery areas usingX-ray imaging to maintain proper dosage levels in the affected areas.

[0047] Accordingly, the placement of markers within the seed can assistin not only determining the orientation of seeds, but alsodifferentiating among the different types of radioisotopes and levels ofactivity among particular implanted seeds. This is done bydifferentiating the different types of radioactive seeds using differentX-ray marker configurations which are detectable using X-ray imaging. Itis in this manner that the multiple markers in radioactive seeds asillustrated with reference to FIGS. 7a through 7 d provide a previouslyunavailable system for monitoring the distribution of the activity ofdosages in a patient's tissue during brachytherapy.

[0048] The radioactive seeds illustrated in FIGS. 7a through 7 d havingdifferent radioisotopes and dosages may also be manufactured using auniform manufacturing process. The process of manufacturing aradioactive seed for a particular radioisotope and a particular dosageis differentiated from the processes of the other types of radioactiveseeds by the selection of appropriate carrier elements for thecorresponding radio isotope and dosage level, and the placement of X-raymarkers among the selected carrier elements within the capsule. Thisenables a single manufacturer to cost effectively provide the differenttypes of radioactive seeds (i.e., having the particular radio isotopeand dosage level) which are distinguishable using X-ray photography.Moreover, the treatment clinic can purchase the different radioactiveseeds from a single vendor, simplifying a system employing differenttypes of radioactive seeds at different dosage levels and radioisotopetypes. This offers distinct advantages over such a systems which wouldrequire the purchase of radioactive seeds from multiple manufacturers toprovide differentiated radioactive seeds. With a system of seeds withmultiple markers from a single manufacturer, such as those shown inFIGS. 7a through 7 d, having X-ray detectable marker configurationsindicative of the activity level or isotope type, the inconvenience ofpurchasing from multiple vendors is avoided.

[0049] While the description above refers to particular embodiments ofthe present invention, it will be understood that many modifications maybe made without departing from the spirit thereof. The accompanyingclaims are intended to cover such modifications as would fall within thetrue scope and spirit of the present invention.

[0050] The presently disclosed embodiments are therefore to beconsidered in all respects as illustrative and not restrictive, thescope of the invention being indicated by the appended claims, ratherthan the foregoing description, and all changes which come within themeaning and range of equivalency of the claims are therefore intended tobe embraced therein.

What is claimed is:
 1. A radioactive seed for use in radiation therapy,the radioactive seed comprising: a sealed housing having an internalcavity; at least one carrier body disposed within the cavity formaintaining a radioisotope, as a radiation source, in a distributionalong a length of the cavity; and a plurality of X-ray detectablemarkers distributed along the length of the cavity, at least two of theX-ray detectable markers being laterally separated from one another byat least one carrier body, wherein the distribution of the plurality ofX-ray markers reveals an orientation of the radioactive seed when theseed is exposed to an X-ray photography.
 2. The radioactive seed ofclaim 1, wherein each of the plurality of X-ray detectable markers has asubstantially spherical shape.
 3. The radioactive seed of claim 2,wherein the radioactive seed is manufactured by rolling the plurality ofX-ray detectable markers into the internal cavity.
 4. The radioactiveseed of claim 1, wherein the carrier body comprises a plurality ofseparate carrier units such that each of the separate carrier units isimpregnated with the radioisotope.
 5. The radioactive seed of claim 4,wherein each of the plurality of separate carrier units is substantiallyevenly distributed along the length of the cavity so that the seed emitssubstantially uniform radiation around the housing of the seed.
 6. Theradioactive seed of claim 4, wherein each of the separate carrier unitshas a substantially spherical shape.
 7. The radioactive seed of claim 6,wherein the radioactive seed is manufactured by rolling the plurality ofseparate carrier units into the internal cavity to facilitate themanufacturing process.
 8. The radioactive seed of claim 4, wherein theplurality of separate carrier units is distributed at one end of thecavity, and the plurality of X-ray detectable markers is distributed atan opposing end of the cavity.
 9. The radioactive seed of claim 1,wherein the housing comprises a material selected from a group oftitanium, plastic, ceramic and stainless steel.
 10. The radioactive seedof claim 1, wherein the radioisotope comprises a material selected froma group of iodine-125 and palladium-103.
 11. The radioactive seed ofclaim 1, wherein the carrier body comprises an ion exchange resinmaterial.
 12. A radioactive seed for use in radiation therapy, theradioactive seed comprising: a sealed housing having an internal cavity;at least one carrier body disposed within the cavity for maintaining aradioisotope, as a radiation source, in a distribution along a length ofthe cavity; and a plurality of X-ray detectable markers distributedalong the length of the cavity adjacent the at least one carrier body,wherein the distribution of the plurality of X-ray markers reveals anorientation of the radioactive seed when the seed is exposed to an X-rayphotography, and wherein each of the plurality of X-ray detectablemarkers has a hole passing through the marker so that radiation from theradioisotope will pass through the X-ray detectable markers.
 13. Aradioactive seed for use in radiation therapy, the radioactive seedcomprising: a sealed container having a cavity; a plurality of carrierssubstantially evenly distributed and laterally spaced along the lengthof the cavity, each of the plurality of carriers containing andmaintaining a radioisotope as a radiation source; and a plurality ofX-ray detectable markers distributed among the carriers such that thedistribution of the markers discloses the orientation of the seed whenthe seed is exposed to X-ray photography, wherein at least two of theX-ray detectable markers are laterally separated from one another by acarrier.
 14. A radioactive seed for use in radiation therapy, theradioactive seed comprising: a sealed housing having an external surfaceand an internal cavity; at least one carrier body disposed within thecavity for maintaining a radioisotope, as a radiation source, in adistribution along a length of the cavity; and an X-ray detectablemarker disposed on and wrapped around the external surface of thehousing in a spiral pattern.
 15. The radioactive seed of claim 13,wherein the X-ray detectable marker discloses the orientation and thelocation of the seed when the seed is exposed to X-ray photography. 16.The radioactive seed according to claim 1, wherein uniformity ofradiation emitted from the housing is only slightly effected by thedistribution of the plurality of X-ray detectable markers.
 17. Theradioactive seed according to claim 13, wherein uniformity of radiationemitted from the housing is only slightly effected by the distributionof the plurality of X-ray detectable markers.
 18. A radioactive seed foruse in radiation therapy, the radioactive seed comprising: a sealedhousing having an internal cavity; at least one carrier body disposedwithin the cavity for maintaining a radioisotope, as a radiation source,in a distribution along a length of the cavity; and a plurality of X-raydetectable markers distributed along the length of the cavity, at leasttwo of the X-ray detectable markers being adjacent to one another,wherein the distribution of the plurality of X-ray markers reveals anorientation of the radioactive seed when the seed is exposed to an X-rayphotography.
 19. A radioactive seed for use in radiation therapy, theradioactive seed comprising: a sealed container having a cavity; aplurality of carriers substantially evenly distributed and laterallyspaced along the length of the cavity, each of the plurality of carrierscontaining and maintaining a radioisotope as a radiation source; and aplurality of X-ray detectable markers distributed among the carrierssuch that the distribution of the markers discloses the orientation ofthe seed when the seed is exposed to X-ray photography, wherein at leasttwo of the X-ray detectable markers are adjacent to one another.
 20. Amethod of treating an affected region of diseased tissue in a patient,the method comprising: implanting a plurality of first radioactive seedsin the affected region, each of the first radioactive seeds having asealed housing with an internal cavity, at least one carrier bodydisposed within the cavity for maintaining a first radioisotope sourceat a first dosage and a plurality of X-ray detectable markers placedalong a length of the cavity in a first configuration; implanting aplurality of second radioactive seeds in the affected region, each ofthe second radioactive seeds having a sealed housing with an internalcavity, at least one carrier body disposed within the cavity formaintaining a second radioisotope source at a second dosage and aplurality of X-ray detectable markers placed along a length of thecavity in a second configuration distinguishable from the firstconfiguration; generating an X-ray image of the affected regionincluding the first and second radioactive seeds implanted therein, theX-ray image providing representations of the first and secondconfigurations which are visibly distinguishable; and associating eachrepresentation of the'first configuration with a seed having one of thefirst radioisotope source and the first dosage, and associating eachrepresentation of the second configuration with a seed having one of thesecond radioisotope source and the second dosage.
 21. The method ofclaim 20, the method further comprising: selecting the firstradioisotope source to comprise a material including palladium-103 andthe second radioisotope to comprise a material including iodine-125; anddetermining a distribution of palladium 103 dosages in the affectedregion based upon locations of the representations of the firstconfiguration in the X-ray image, and a distribution of the iodine 125in the affected region based upon locations of the representations ofthe second configuration in the X-ray image.
 22. The method of claim 20,the method further comprising: selecting the first dosage to be greaterthan the second dosage; and determining a distribution of the dosage inthe affected region by associating each location of a representation ofthe first configuration in the X-ray image with a seed having the firstdosage and associating each representation of the second configurationin the X-ray image with a seed having the second dosage.
 23. Aradioactive seed for use in radiation therapy, the radioactive seedcomprising: a sealed housing having an internal cavity; at least onecarrier body disposed within the cavity for maintaining a particularradioisotope, as a radiation source, in a distribution along a length ofthe cavity; and a plurality of X-ray detectable markers distributedalong the length of the cavity in a configuration which isrepresentative of the particular radioisotope source, wherein theconfiguration of the plurality of X-ray markers visibly identifies theparticular radioisotope source of the radioactive seed when the seed isexposed to X-ray photography.
 24. The radioactive seed of claim 23,wherein the particular radioisotope source is a material selected asincluding one of iodine-125 and palladium-103.
 25. The radioactive seedof claim 23, wherein at least two of the X-ray markers are adjacent toone another.
 26. The radioactive seed of claim 23, wherein at least twoof the X-ray markers are laterally separated from one another.
 27. Aradioactive seed for use in radiation therapy, the radioactive seedcomprising: a sealed housing having an internal cavity; at least onecarrier body disposed within the cavity for maintaining a radioisotope,as a radiation source at a particular dosage level, in a distributionalong a length of the cavity; and a plurality of X-ray detectablemarkers distributed along the length of the cavity in a configurationwhich is representative of the particular dosage level, wherein theconfiguration of the plurality of X-ray markers visibly identifies theparticular dosage level of the radioactive seed when the seed is exposedto X-ray photography.
 28. The radioactive seed of claim 27, the whereinat least two of the X-ray markers are adjacent to one another.
 29. Theradioactive seed of claim 27, wherein at least two of the X-ray markersare laterally separated from one another.